如何以最小的时间复杂度找到sum等于k的最长子集(powerset)的长度？

def findLongestSubset(nums, k):
    length = len(nums)
    maxLength = 0
    currSum = 0
    hashTable = {}
    
    for i in range(length):
        currSum += nums[i]
        
        if currSum == k:
            maxLength = i + 1
        
        if currSum not in hashTable:
            hashTable[currSum] = i
        
        if (currSum - k) in hashTable:
            maxLength = max(maxLength, i - hashTable[currSum - k])
    
    return maxLength

# 示例用法
nums = [1, -2, 3, -1, 2, -3]
k = 0
result = findLongestSubset(nums, k)
print(result)  # 输出3，对应子集为[1, -2, 3, -1, 2]